20200707: 这个更好 https://github.com/redisson/redisson
仅供个人记录
工具类：
RedisLock.java
import lombok.extern.slf4j.Slf4j;
/**
* 分布式锁工具类.
* @author Pete.Lee Aug 29, 2017 3:23:41 PM
*/
@Slf4j
public class RedisLock {
private static final int DEFAULT_ACQUIRY_RESOLUTION_MILLIS = 100;
private final String lockKey;
/**
* 锁超时时间，防止线程在入锁以后，无限的执行等待
*/
private int expireMsecs = 120 * 1000;
/**
* 锁等待时间，防止线程饥饿
*/
private int timeoutMsecs = 20 * 1000;
private volatile Boolean locked = false;
private String myExpires = "";
public RedisLock(final String lockKey) {
this.lockKey = lockKey + "_lock";
}
public RedisLock(final String lockKey, final int timeoutMsecs) {
this(lockKey);
this.timeoutMsecs = timeoutMsecs;
}
public RedisLock(final String lockKey, final int timeoutMsecs, final int expireMsecs) {
this(lockKey, timeoutMsecs);
this.expireMsecs = expireMsecs;
}
public String getLockKey() {
return lockKey;
}
/**
* 获得 lock. 实现思路: 主要是使用了redis 的setnx命令,缓存了锁. reids缓存的key是锁的key,所有的共享, value是锁的到期时间(注意:这里把过期时间放在value了,没有时间上设置其超时时间)
* 执行过程: 1.通过setnx尝试设置某个key的值,成功(当前没有这个锁)则返回,成功获得锁 2.锁已经存在则获取锁的到期时间,和当前时间比较,超时的话,则设置新的值
* @return true if lock is acquired, false acquire timeouted
* @throws InterruptedException in case of thread interruption
*/
public synchronized Boolean lock() throws InterruptedException {
int timeout = timeoutMsecs;
while (timeout >= 0) {
final long expires = System.currentTimeMillis() + expireMsecs + 1;
final String expiresStr = String.valueOf(expires); // 锁到期时间
if (RedisUtil.setNx(lockKey, expiresStr)) {
// lock acquired
myExpires = expiresStr;
locked = true;
return true;
}
final String currentValueStr = RedisUtil.get(lockKey); // redis里的时间
if (currentValueStr != null && Long.parseLong(currentValueStr) < System.currentTimeMillis()) {
//判断是否为空，不为空的情况下，如果被其他线程设置了值，则第二个条件判断是过不去的
// lock is expired
final String oldValueStr = RedisUtil.getSet(lockKey, expiresStr);
//获取上一个锁到期时间，并设置现在的锁到期时间，
//只有一个线程才能获取上一个线上的设置时间，因为jedis.getSet是同步的
if (oldValueStr != null && oldValueStr.equals(currentValueStr)) {
//防止误删（覆盖，因为key是相同的）了他人的锁——这里达不到效果，这里值会被覆盖，但是因为什么相差了很少的时间，所以可以接受
//[分布式的情况下]:如过这个时候，多个线程恰好都到了这里，但是只有一个线程的设置值和当前值相同，他才有权利获取锁
// lock acquired
myExpires = expiresStr;
locked = true;
return true;
}
}
timeout -= DEFAULT_ACQUIRY_RESOLUTION_MILLIS;
/*
延迟100 毫秒, 这里使用随机时间可能会好一点,可以防止饥饿进程的出现,即,当同时到达多个进程,
只会有一个进程获得锁,其他的都用同样的频率进行尝试,后面有来了一些进行,也以同样的频率申请锁,这将可能导致前面来的锁得不到满足.
使用随机的等待时间可以一定程度上保证公平性
*/
Thread.sleep(DEFAULT_ACQUIRY_RESOLUTION_MILLIS);
}
return false;
}
public synchronized void unlock() {
// 如果当前redis中的锁与上锁相同删除锁
if (myExpires.equals(RedisUtil.get(lockKey))) {
if (locked) {
RedisUtil.del(lockKey);
locked = false;
}
}
}
}
RedisUtil.java
import lombok.extern.slf4j.Slf4j;
import org.springframework.data.redis.connection.RedisConnection;
import org.springframework.data.redis.core.StringRedisTemplate;
import org.springframework.data.redis.serializer.StringRedisSerializer;
import java.util.ArrayList;
import java.util.List;
/**
* redis 工具类.
* @author Pete.Lee 2017/9/5 15:01
*/
@Slf4j
public class RedisUtil {
private static StringRedisTemplate template = ContextUtil.getBean("StringRedisTemplate", StringRedisTemplate.class);
public static String get(final String key) {
String obj = null;
try {
obj = template.execute((final RedisConnection c) -> {
final StringRedisSerializer serializer = new StringRedisSerializer();
final byte[] data = c.get(serializer.serialize(key));
c.close();
return serializer.deserialize(data);
});
} catch (Exception ex) {
log.error("get redis error, key : {}", key);
}
return obj;
}
public static Boolean setNx(final String key, final String value) {
Boolean b = false;
try {
b = template.execute((final RedisConnection c) -> {
final StringRedisSerializer serializer = new StringRedisSerializer();
final Boolean success = c.setNX(serializer.serialize(key), serializer.serialize(value));
c.close();
return success;
});
} catch (Exception e) {
log.error("setNX redis error, key : {}", key);
}
return b;
}
public static String getSet(final String key, final String value) {
String obj = null;
try {
obj = template.execute((final RedisConnection c) -> {
final StringRedisSerializer serializer = new StringRedisSerializer();
final byte[] ret = c.getSet(serializer.serialize(key), serializer.serialize(value));
c.close();
return serializer.deserialize(ret);
});
} catch (Exception ex) {
log.error("setNX redis error, key : {}", key);
}
return obj;
}
public static Boolean del(final String key) {
Boolean obj = null;
try {
obj = template.execute((final RedisConnection c) -> {
final StringRedisSerializer serializer = new StringRedisSerializer();
return c.del(serializer.serialize(key)) > 0;
});
} catch (Exception ex) {
log.error("del redis error, key : {}", key);
}
return obj;
}
public static Long leftPush(final String key, final String value) {
return template.opsForList().leftPush(key, value);
}
public static Long rightPush(final String key, final String value) {
return template.opsForList().rightPush(key, value);
}
public static String leftPop(final String key) {
return template.opsForList().leftPop(key);
}
public static String rightPop(final String key) {
return template.opsForList().rightPop(key);
}
/*public RedisUtil() {
final JedisConnectionFactory factory = new JedisConnectionFactory();
factory.setHostName("xxxx");
factory.setPort(6379);
factory.setDatabase(2);
factory.afterPropertiesSet();
template = new StringRedisTemplate(factory);
template.afterPropertiesSet();
// System.out.println(template.boundValueOps("自增Key").increment(1));
}*/
}
RedisConfigure.java
import com.fasterxml.jackson.annotation.JsonAutoDetect;
import com.fasterxml.jackson.annotation.JsonInclude;
import com.fasterxml.jackson.annotation.PropertyAccessor;
import com.fasterxml.jackson.databind.ObjectMapper;
import com.fasterxml.jackson.databind.SerializationFeature;
import com.fasterxml.jackson.datatype.joda.JodaModule;
import com.fasterxml.jackson.datatype.joda.cfg.JacksonJodaDateFormat;
import com.fasterxml.jackson.datatype.joda.ser.DateTimeSerializer;
import org.joda.time.DateTime;
import org.springframework.cache.annotation.EnableCaching;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.data.redis.connection.RedisConnectionFactory;
import org.springframework.data.redis.core.RedisTemplate;
import org.springframework.data.redis.core.StringRedisTemplate;
import org.springframework.data.redis.serializer.Jackson2JsonRedisSerializer;
import org.springframework.data.redis.serializer.StringRedisSerializer;
import org.springframework.format.annotation.DateTimeFormat;
import org.springframework.format.datetime.joda.DateTimeFormatterFactory;
import java.util.TimeZone;
@Configuration
@EnableCaching
public class RedisConfigure {
@Bean(name = "StringRedisTemplate")
public RedisTemplate normalRedisTemplate(final RedisConnectionFactory factory,
final ObjectMapper jodaMapper) {
final StringRedisSerializer keySerializer = new StringRedisSerializer();
final Jackson2JsonRedisSerializer valueSerializer = new Jackson2JsonRedisSerializer<>(Object.class);
valueSerializer.setObjectMapper(jodaMapper);
final RedisTemplate template = new RedisTemplate<>();
template.setConnectionFactory(factory);
template.setKeySerializer(keySerializer);
template.setHashKeySerializer(keySerializer);
template.setValueSerializer(valueSerializer);
template.setHashValueSerializer(valueSerializer);
template.afterPropertiesSet();
return template;
}
@Bean
public ObjectMapper jodaMapper() {
final ObjectMapper om = new ObjectMapper();
final JodaModule jodaModule = new JodaModule();
final DateTimeFormatterFactory formatterFactory = new DateTimeFormatterFactory();
formatterFactory.setPattern("yyyy-MM-dd'T'HH:mm:ss.SSSZ");
formatterFactory.setIso(DateTimeFormat.ISO.DATE);
jodaModule.addSerializer(DateTime.class, new DateTimeSerializer(
new JacksonJodaDateFormat(formatterFactory.createDateTimeFormatter())));
om.setSerializationInclusion(JsonInclude.Include.NON_NULL);
om.registerModule(jodaModule);
om.disable(SerializationFeature.WRITE_DATES_AS_TIMESTAMPS);
om.setTimeZone(TimeZone.getTimeZone("GMT+8"));
return om;
}
}
ContextUtil.java
import org.springframework.beans.BeansException;
import org.springframework.context.ApplicationContext;
import org.springframework.context.ApplicationContextAware;
import org.springframework.stereotype.Component;
/**
* 获取Bean工具类.
* @author Pete.Lee 2017/9/5 15:02
*/
@Component
public class ContextUtil implements ApplicationContextAware {
private static ApplicationContext context;
@Override
public void setApplicationContext(ApplicationContext applicationContext) throws BeansException {
ContextUtil.context = applicationContext;
}
public static ApplicationContext getContext() {
return context;
}
public static T getBean(final String name, final Class requiredType) {
return context.getBean(name, requiredType);
}
}
YAML
spring:
redis:
host: 10.20.9.85
port: 6379
database: 0
password:
pool.max-idle: 8
pool.min-idle: 4
pool.max-active: 16
pool.max-wait: -1
应用
final RedisLock lock = new RedisLock("lottery_result");
while (true) {
try {
if (lock.lock()) {
// 需要加锁的代码
}
} catch (InterruptedException ex) {
} finally {
lock.unlock();
}
}
这个说的更详细
https://www.cnblogs.com/wlwl/p/11651409.html